Art of precision surface abrading



p 1, 19% A. J. HACKMAN, JR 3,526,057

ART OF PRECISION SURFACE ABRADING Filed Feb. 14, 1968 H/S A TTORNEYUnited States Patent 3,526,057 ART OF PRECISION SURFACE ABRADING ArthurJ. Hackman, Jr., Grosse Pointe, Mich., assignor of one-half to GenevieveI. Hanseom (formerly Genevieve I. Magnuson), and one-half to GenevieveI. Hanscom, Robert Magnuson, and Lois J. Thomson (formerly Lois J.Duggan) as trustees of the estate of Roy M. Magnuson Filed Feb. 14,1968, Ser. No. 705,505 Int. 'Cl. B24b 27/00 US. Cl. 51-1 12 ClaimsABSTRACT OF THE DISCLOSURE Lap size changing means are providedcomprising an axially tapered lap holding part which is capable ofradially expanding or contracting, said lap holding part having means tohold in axially fast relationship to itself a lap which is capable ofradially expanding or contracting with said lap holding part, means formoving an axially tapered arbor in respect to the axial taper on saidlap holding part to radially expand or contract said lap holding part,means for maintaining said lap holding part axially stationary duringits radial expansion or contraction so that said lap radially expands orcontracts with said lap holding part without changing the relative axialposition of said lap in respect to a workpart said lap is abrading,whereby the radial expansion or contraction of said lap can beaccomplished while said lap is in the process of abrading said workpart.

My invention relates to the art of precision surface abrading by whichis meant that art which is capable of producing finishes on metalworkparts including geometries thereof to tolerances in the millionthsof an inch.

In this art a lap and workpart are held in concentric frictionalengagement and moved relative to each other so that the lap carries outa precision surface abrading operation on a surface of the workpart.Such relative movement comprises either relative rotation or relativeaxial reciprocation and wherever possible the two togethersimultaneously. Such relative axial reciprocation is preferably cyclicand oppositely equal and uniform in extent and speed. This type ofrelative axial reciprocation simultaneously with such relative rotationof a lap and workpart is best accomplished by the means and methoddisclosed in my US. Pat. 3,247,622 issued Apr. 26, 1966. (See also mycopending application Ser. No. 544,940 now US. Pat. 3,462,887 issuedAug. 26,1969.) In each of these cases the precision surface abradingoperation must be stopped periodically at intervals whenever the lap andthe workpart become loose by reason of metal removal from said workpart.The radial dimensions of the lap must be changed to bring the lapsurface into tight frictional engagement with the workpart surface, i.e.so that the lap exerts sufiicient pressure on the workpart to abrade thesame, and this is accomplished during interruption of such precisionsurface abrading operation but while the lap and workpart are held inconcentric frictional engagement with each other to prevent overchangingthe radial dimensions of the lap. Following such radially changing insize of the lap the precision surface abrading operation is repeateduntil the lap surface needs to be made tight again with the workpartsurface whereupon the precision surface abrading operation is againinterrupted. The foregoing procedure of alternately carrying out aprecision surface abrading operation and radially changing the size ofthe lap is continued until the workpart is finished to the desireddimensions including roundness, straightness and surface finish.

Patented Sept. 1, 1970 I have devised means and method which eliminatethe foregoing procedure and obviate the need to interrupt the precisionsurface abrading operation in order to radially change the size of thelap to bring its lap surface into tight frictional engagement with theworkpart surface. The provision of .such means and method by which thelap may be dimensionally changed radially while it is carrying out aprecision surface abrading operation on the workpart is the principalobject of my invention. Such object and the advantages of my inventionwill become apparent during the course of the following descriptiontaken in conjunction with the accompanying drawings in which:

FIGS.= l to 10 are views of lap size changing means and method embodyingmy invention; FIGS. 1 to 8 being views of a lap size changing internallyand externally tapered hollow sleeve shown in operative relation with anhelically slotted internally tapered lap and an extenrally taperedarbor; and FIGS. 9 and 10 being views of machine parts for changing therelative axial positions of said sleeve and arbor and hence of said lapwhile said lap is carrying out a precision surface abrading operation ona workpart.

Referring to the drawings in greater detail, 12 designates .the taperedarbor, the free end of which is uniformly tapered. A cylindricalenlargement having a transverse bore 14 therethrough is provided on therear end of the arbor 12 which enlargement has formed thereon inwardlyof the rear face thereof a threaded aperture 15. The purpose of the bore14 and aperture 15 will appear later. The tapered free end of the arbor12 carries the size changing hollow sleeve which is designated 16. Thesleeve 16 has an annular body to the free end of which is uniformlydouble tapered corresponding to the taper on the arbor 12, i.e. it isprovided with both an internal taper and an external taper of the samedirection. A cylindrical enlargement, the purpose of which will appear,is provided on the rear end of the sleeve .16. The double tapered freeend of the sleeve 16 is provided with a through-slot constructionthrough its annular wall so that it will change its dimensions radiallyin accordance with its relative axial position on the arbor 12. In theinstance the free end of the sleeve 16 is split axially by fourcircumferentially equally spaced through slots 18 which extendlogitudinally over the greater part of the length of the free end of thesleeve 16. The free end of the sleeve 16 carries an internal lap 20having an annular body, the external surface of which is cylindrical orstraight for lapping internal surfaces of workparts. The lap 20 is ofthe smooth surfaced type which employe a free abrasive compound asmentioned in said US. Pat. 3,247,622 and in said application S.N.544,940 now US. Pat. 3,462,887 issued Aug. 26, 196 9. The lap 20 may beprovided with different forms on its external surface other than thecylindrical or straight form shown. Such external surface of the lap 20carries a diamond pattern of degrees phase shifted helical grooves 21 torender more effective its lapping action with such free abrasivecompound. In spite of such patterned external surface the lap 20 isstill characterized as a smooth surfaced lap as shown and described insaid prior US. Pat. 3,247,622 in contrast to a diamond abrasive coatedlap as shown and described in said prior co-pending application S.N.544,940 now US. Pat. 3,462,887 issued Aug. 26, 1969. The internalsurface of the lap 20 is tapered corresponding to the taper on the arbor12. The body of the lap 20 has a through-slot construction through itsannular wall preferably extending the length of the lap which, in theinstance, is in the form of a helical slot 22 spiraling about 360degrees from one end of the lap to the other. The lap 20 may be straightslotted in certain instances.

Shifting of the axial position of the arbor 12 in respect to the sleeve16 changes the radial dimensions of the sleeve 16 and hence of the lapas no relative movement occurs between the lap 20 and the sleeve 16. Asthe arbor 12 is shifted axially within the sleeve 16 from the positionshown in FIG. 1 to that in FIG. 2 it carries to lap 20 therewith and theradial dimensions of the latter are increased. As the arbor 12 isaxially shifted within the sleeve 16 from the position shown in FIG. 2to that in FIG. 1 the radial dimensions of the lap 20 decrease. Axialshifting of the arbor 12 within the sleeve 16 automatically while thelap 20 is carrying out a precision surface abrading operation on aworkpart may be accomplished, eg, via the machine parts shown in FIGS. 9and 10. In these figures parts of a precision surface abrading machine,such as the abrading machine described and claimed in my said US. Pat.3,2A7,622, are shown in which W is a workpart carried on a workholder(not shown), such as the workholder 105 shown in said Pat. 3,247,622(the workholder 105 must be modified as explained hereinafter), andsupported for cyclic axial reciprocation in the tailstock 18 of saidabrading machine. The headstock of said abrading machine is designated23 in these figures and supports via bearings 25 a rotatably drivenshaft 24 which carries the arbor 12 so that the sleeve 16 and the lap 20on the free end thereof rotates within the cyclicly axiallyreciprocating workpart W. The shaft 24 is provided with a bore 26 whichextends inwardly therein from its rear in which bore 26 the arbor 12 isslidably supported via the enlargement on the rear end thereof. Thearbor 12 is movably axially of the shaft 24 by a double actinghydraulically or pneumatically operated ram 28 the front end of which isprovided with a threaded stud 29 threadably engaged in the aperture 15.Rotary drive from the shaft 24 to the arbor 12 is transmitted by a rod30 which extends through the bore 14 in the enlargement on the rear endof said arbor 12 and into diameterically disposed through-slots 32 inthe annular portion of the shaft 24 surrounding the bore 26. The rod 30moves in the slots 32 while it transmits such rotary drive while thearbor 12 is being moved by the ram 28 axially in respect to the shaft24. The front end of the shaft 24 captures the sleeve 16 against axialmovement relative thereto via a bore 34 in which the enlargement on therear end of the sleeve .16 is disposed and via a washer 33 and a coverplate 35 which is bolted by fasteners 36 to the front end of the shaft24. The lap 20 may be removed from the sleeve 16 as often as desired tochange laps but the sleeve 16 cannot be removed from the arbor 12without unfastening the cover plate 35 and removing the washer 33. Therotary drive applied to the arbor 12 is transmitted to the sleeve 16 byvirtue of its frictional engagement with said sleeve 16. (The sleeve 16is free to rotate in respect to the shaft 24 which feature is utilizedin the event the lap 20 becomes too tight and does not rotate in respectto the Workpart W which event will hold the sleeve 16 fast causing thearbor 12 to slip inside the sleeve 16.) The sleeve 16 in turn rotatablydrives the lap 20 by virtue of the frictional engagement of the latterwith said sleeve 16. While the lap 20 is carrying out a precisionsurface abrading operation on the workpart W its radial dimensions maybe increased by movement of the ram 28 (and hence of the arbor .12 andthe lap 20) axially and outwardly of the shaft 24 in the direction fromthe position shown in FIG. 9 to that in FIG. 10. Movement of the ram 28whether actuated by pneumatic or hydraulic power must be under manualcontrol for the operator of the lapping machine to feel the tightness ofthe lap 20 within the workpart W. Such increase of the radial dimensionsof the lap 20 is accomplished periodically during such abradingoperation while the workpart W is cyclically reciprocated over the lap20 and in such increments as to compensate for the amount of metalremoval from the internal bore of the workpart W to insure that the lap20 exerts sufficient pressure on the workpart W to abrade the same. Theworkholder for the workpart W must be modified from the workholder shownin said US. Pat. 3,247,622 to eliminate the bushing in its barrel 122 sothat the arbor 12 can project through such barrel 122 without anyinterference. With the means and method described there is no need tostop the lapping machine to adjust the size of the lap as had to be doneheretofore every 5 seconds or so. Now the lap is initially expanded byaxially moving the arbor 12 in respect to the sleeve 16 until the lap 20is tight within the bore of the workpart W. The lapping machine is thenstarted and the lap 20 is expanded periodically every 2 or 3 seconds orso to maintain the lap 20 in tight frictional engagement with theworkpart W while the machine is operating and while the lap 20 iscarrying out a precision surface abrading operation on the workpart W.The lapping machine is then stopped: (a) at the end of the predeterminedlapping time if the workpart W is a production workpart on which a timecycle has been worked out; or (b) after a predetermined amount of lapexpansion if the lapping machine is equipped with an indicator todetermine the relative axial position of the lap 20 and the arbor 12; or(c) if the lapping machine is not so equipped, to gage the workpart W.In the case of the ram 28 its axial position relative to the shaft 24(and hence the axial position of the lap 20 and the sleeve 16 relativeto the arbor 12) can be indicated by suitable indicator means (notshown) in which case the lap 20 may be expanded every 20 millionths ofan inch or so of expansion in diameter while the lap 20 is rapidlyrotating within the cyclicly reciprocating workpart W carrying out aprecision surface abrading operation on the latter. If a handwheelsimilar to the handwheel 29 in said US. Pat. 3,247,622 were employed inlieu of the ram 28 to axially move the arbor 12 relative to the shaft24, and to the sleeve .16 the indicator 35 shown in said US. Pat.3,247,- 622 could be used without much modification to indicate theamount of lap expansion.

It will thus be seen that there has been provided by my presentinvention lap size changing means and method in which the advantageshereinabove set forth together with many other thoroughly practicaladvantages have been successfully achieved. While a preferred embodimentof my invention has been shown and described it is to be understood thatvariations and changes may be resorted to without departing from thespirit of my invention as defined by the appended claims. For example,my invention may be applied by the principles herein taught to radiallychange the dimensions of an external lap while it is carrying out aprecision surface abrading operation on a workpart.

What is claimed is:

1. In the art of precision surface abrading, lap size changing meanscomprising an axially tapered lap holding part which is capable ofradially expanding or contracting, said lap holding part having means tohold in axially fast relationship to itself a lap which is capable ofradially expanding or contracting with said lap holding part, an axiallytapered arbor means for moving said axially tapered arbor in respect tothe axial taper on said lap holding part to radially expanding orcontract said lap holding part, means for maintaining said lap holdingpart axially stationary during its radial expansion or contraction sothat said lap radially expands or contracts with said lap holding partwithout changing the relative axial position of said lap in respect to aworkpart said lap is abrading, whereby the radial expansion orcontraction of said lap can be accomplished while said lap is in theprocess of abrading said workpart.

2. Lap size changing means as claimed in claim 1 in which said lapholding part is doubly axially tapered and said lap is held axially fastin respect to said lap holding part by the other axial taper thereonthan the one used to radially expand or contract said lap holding part.

3. Lap size changing means as claimed in claim 2 in which said lapholding part is both internally and externally axially tapered and isradially expanded or contracted via its internal taper and holds saidlap axially fast via its external taper.

4. Lap size changing means as claimed in claim 3 in which said lapholding part has such an annular wall thickness as to be in form asleeve, said sleeve being longitudinally slotted inwardly from its frontend and having holding means on its rear end by which it can be heldaxially stationary during its radial expansion or contraction.

5. Lap size changing means as claimed in claim 1 further comprisingmeans for applying a rotatable driving force to said arbor to rotatablydrive said lap holding part and said lap held thereby.

6. In the art of precision surface abrading, lap size changing meanscomprising a lap holding part which is both internally and externallyaxially tapered and is capable of being radially expanded or contractedvia one of said tapers, said lap holding part capable of holding inaxially fast relationship thereto via the other of said tapers a lapcapable of radially expanding or contracting with said lap holding part,said lap holding part having means by which it can be held axiallystationary while it is being radially expanded or contracted so thatsaid lap .does not change its axial position in relationship to theworkpart it is abrading whereby the radial expansion or contraction ofsaid lap can be accomplished while said lap is in the process ofabrading said workpart.

7. Lap size changing means as claimed in claim 6 in which said lapholding part is radially expanded or contracted via its internal taperand holds said lap axially fast via its external taper.

8. Lap size changing means as claimed in claim 7 in which said lapholding part has such an annular wall thickness as to be in form asleeve, said sleeve being longitudinally slotted inwardly from its frontend and having holding means on its rear end by which it can be heldaxially stationary during its radial expansion or contraction.

9. In the art of precision surface abrading, lap size changing methodcomprising holding a lap in axially fast relationship to an axiallytapered lap holding part, axially moving an axially tapered arbor inrespect to the axial taper on said lap holding part to radially expandor contract said lap holding part while maintaining said lap holdingpart axially stationary so that said lap radially expands or contractswith said lap holding part lap holding part axially stationary so thatsaid lap in respect to a workpart said lap is abrading, whereby theradial expansion or contraction of said lap can be accomplished whilesaid lap is in the process of abrading said workpart.

10. Lap size changing method as claimed in claim 9 in which said lap isheld axially fast in respect to said lap holding part by an axial taperon said lap holding part by an axial taper on said lap holding partother than the one used to radially expand or contract said lap holdingpart.

11. Lap size changing method as claimed in claim 10 in which said lapholding part is radially expanded or contracted via an internal taperthereon and in which said lap is held axially fast on said lap holdingpart via an external taper thereon.

12. Lap size changing method as claimed in claim 11 in which a rotatabledriving force is applied to said arbor to rotatably drive said lapholding part and said lap held thereby.

References Cited UNITED STATES PATENTS 1,583,010 5/1926 Richardson 51-12,044,474 6/1936 Groetchen 51-1 2,767,676 10/1956 Johnson et al. 269-4813,247,622 4/1966 Hackman 51--l65 OTHELL M. SIMPSON, Primary Examiner US.Cl. X.R. 51-72 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3,526,057 September 1, 1970 Arthur J. Hackman, Jr.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column Column 2, line 49, "employe" should read employs line 3, line 31,"movably" should read moveable Column 4, 60, after "arbor" insert acomma; line 62, "expanding" should read expand Column 6, line 8, "lapholding part axially stationary so that" should read without changingthe relative axial position of line 17, cancel "by an axial taper onsaid lap holding part".

Signed and sealed this 16th day of March 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

